Theory of Liquid Ink Development in Electrophotography

When an electric field is present across two different fluid dielectrics having a common plane boundary, some disturbances in the interfacial boundary are found to grow in time. The liquid ink development process is viewed as the result of varying instability of the oil-ink interface as a function of the differing field gradient in light and dark areas of the exposed image. In an analysis of the disturbances into normal modes, the theory relates the effects upon instability due to potential difference across the oil, the surface tension, the respective viscosities of the oil and the ink, and the finite thicknesses of the oil, ink, and the photoconductor layer. The threshold potential difference for the onset of instability is also given.